Common rail fuel systems have shown considerable promise in providing the versatility necessary to improve performance while also reducing undesirable emissions, especially in relation to compression ignition engines. As the industry demands ever more performance capabilities at a wide variety of engine operating conditions, new problems have arisen. For instance, in order to produce the lowest possible emissions during a combustion event, fuel injectors are often called upon to have the ability in inject relatively large volumes and extremely small volumes of fuel, sometimes in the same sequence involving a main injection event followed closely by a closed coupled post injection event. Being able to accurately inject different volumes of fuel in a broad range at precise timings using a fuel injector in a limited spatial envelope may require great attention to materials utilized and structures associated with the solenoid assembly used to control injection events. In addition, these assemblies must be robust and consistent in the hostile environment of an internal combustion engine.
One example fuel injector is described in co-owned U.S. Patent Publication 2010/0176223, which shows a common rail fuel injector that utilizes a direct operated check valve that is controlled by a two-way needle control valve. The needle control valve opens and closes a needle control chamber to a low pressure passageway connected to a drain outlet by energizing and de-energizing, respectively, a solenoid actuator. Among other things, this reference demonstrates that many variables must be considered and a host of choices made in order to arrive at a solenoid assembly recipe that meets all of the performance, life expectancy, consistency and other specifications associated with a real combination of hardware that can perform as expected in a real internal combustion engine, and be manufacturable in mass quantities at a competitive cost.
The present disclosure is directed toward one or more of the problems set forth above.